1. Field of the Invention
The present invention relates to a Liquid-Crystal Display (LCD) device and a method of fabricating the same and more particularly, to a LCD device comprising markers which are used in the attachment or placement operation of an optical element to a LCD panel, and a method of fabricating the device.
2. Description of the Related Art
In recent years, the LCD device has been extensively used as small-sized display devices such as projector apparatuses, portable telephones, and so on, rapidly by exploiting its characteristics of low power dissipation, small weight, and thinness. If an optical element such as a lens is attached to the LCD panel, highly value-added products may be provided.
To exploit the characteristics of an optical element at the maximum when the element is attached to an LCD panel, it is necessary to attach or place the element to the panel with high positional accuracy. To realize such the high-precision attachment or placement operation as described here, it is required that markers are respectively formed on the panel and element in advance and then, an attachment or placement operation between the panel and the element is performed while reading the markers.
With a LCD panel whose picture-frame region located outside the display region is narrowed (i.e., a LCD panel having a narrowed picture-frame region), there is scarcely an extra space in the outside area of the sealing material and therefore, the markers are disposed in the non-display region formed inside the sealing material. In this case, since two polarizer plates are attached to the each side of the panel in such a way as to cover the sealing material to prevent the leakage of light, the markers are disposed below one of the polarizer plates (i.e., on the side nearer to the liquid crystal layer). The optical element is placed and attached onto the said polarizer plate that has been attached to the LCD panel and thus, the markers on the panel need to be read by way of the polarizer plate or plates.
With the transmissive type LCD device, it is usual that two polarizer plates are respectively attached to the two surfaces of the LCD panel in such a way that their absorption axes are intersected at right angles. Therefore, if this device is designed to operate in the normally black mode, light does not penetrate through the panel unless an ON voltage is applied to the liquid-crystal molecules. Accordingly, there is a problem that the markers on the panel are unable to be read in the placement or attachment operation of the element to the panel. On the other hand, if this device is designed to operate in the normally white mode, light penetrates through the panel without application of an ON voltage to the liquid-crystal molecules. However, alignment films are formed only the inside of the display region. Therefore, similar to the LCD device operating in the normally black mode, there is a problem that the markers formed in the non-display region where the alignment films do not exist are unable to be read.
With the reflective type LCD device, external light which has entered into the incident side of the LCD panel is reflected by the reflective electrodes (or the reflective plates) provided on the opposite side to the incident side of the panel, thereby making it possible to display images. Accordingly, the external light thus entered into the panel penetrates twice through one of the polarizer plates provided on the incident side of the panel, which is different from that of the transmissive type LCD device.
For example, in a case where the reflective type LCD device is designed to operate in the Vertical Aligned (VA) mode, if linearly polarized light enters the LCD panel by way of the entrance-side polarizer plate, the linearly polarized light will penetrate through a quarter wavelength (λ/4) plate (i.e., an optical retardation film) disposed adjacent to the entrance-side polarizer plate to be, for example, left-handed circularly polarized light and then, it will reach the reflective electrodes and reflected by the same. The reflected light generated by the reflection on the reflective electrodes will be, for example, right-handed circularly polarized light and then, will penetrate through the λ/4 plate to be linearly polarized light. Since this linearly polarized light is perpendicular in polarization plane to the incident linearly polarized light, it will be unable to penetrate through the entrance-side polarizer plate unless an ON voltage is applied to the liquid-crystal molecules. Accordingly, with the reflective type LCD device also, there is a problem that the markers are unable to be read in the attachment operation of the optical element to the panel. This is similar to the transmissive type LCD device designed to operate in the normally black mode.
Moreover, with the reflective type LCD device, it is usual that the obtainable contrast due to the reflected light generated by the reflective electrodes is low. Therefore, there is another problem that the markers cannot be recognized with high accuracy.
The semi-transmissive or trans-reflective type LCD device comprises the structure obtained by combining the transmissive type LCD device and the reflective type LCD device together. Therefore, the above-described explanations for the transmissive and reflective type LCD devices are applied to the semi-transmissive type LCD device.
Taking the above-described problems into consideration, a variety of improvements have ever been made so far.
For example, the Japanese Patent No. 3496675 issued on Feb. 16, 2004 discloses a method of fabricating a LCD device. In this method, a polarizer plate located on a driver substrate and a polarizer plate located on an opposite substrate are coupled together in such a way as to have a positional deviation. Marks are formed on the non-overlapped parts of the substrates formed by this deviation. In this way, the marks can be made readable by way of the polarizer plates. FIG. 1 shows the LCD panel disclosed in this Patent.
The LCD panel shown in FIG. 1 comprises an upper glass 101 and a lower glass 102 as a pair of substrates where a liquid crystal is enclosed in the gap between the glasses 101 and 102, an upper polarizer plate 103 attached to the upper glass 101, and a lower polarizer plate 104 attached to the lower glass 102. Four marks 105a, 105b, 105c, and 105d are formed on the lower glass 102. The upper polarizer plate 103 is placed outside the upper glass 101. The lower polarizer plate 104 is placed outside the lower glass 102. The upper and lower polarizer plates 103 and 104 are coupled in such a way as to be deviated from each other at a distance Δ along their longitudinal directions (i.e., along the lateral direction in FIG. 1). The marks 105a, 105b, 105c, and 105d are formed on the non-overlapped parts of the lower glass 102 on the left and right sides. The marks 105a and 105b are disposed on the non-overlapped part on the right side in FIG. 1. The marks 105c and 105d are disposed on the non-overlapped part on the left side in FIG. 1.
In the Japanese Patent No. 3496675, it is said that the marks 105a, 105b, 105c, and 105d can be read with eyes, a CCD (Charge-Coupled Device) camera, or the like, by way of the upper or lower polarizer plate 103 or 104 by disposing the marks 105a, 105b, 105c, and 105d in such the manner as above.
With the LCD panel disclosed in the Japanese Patent No. 3496675, when the upper polarizer plate 103 is attached to the upper glass 101, the end portion of the plate 103 needs to be disposed between the boundary of the display region and the marks 105a and 105b. Moreover, when the lower polarizer plate 104 is attached to the lower glass 102, the end portion of the plate 104 needs to be disposed between the boundary of the display region and the marks 105c and 105d. For this reason, taking the coupling or attachment accuracy of the upper and lower polarizer plates 103 and 104 into consideration, it is inevitable that the marks 105a, 105b, 105c, and 105d are formed to be larger than the display region in such a away as to be on the outside of the display region. Therefore, there is a problem that the distance between the display region and the sealing material for sealing or enclosing the liquid crystal will be enlarged, in other words, the picture-frame region will be widen.
Moreover, since the step or process of accurately deviating the upper and lower polarizer plates 103 and 104 and attaching the same is required, there is another problem that the fabrication cost cannot be lowered.